With development of techniques for the Internet, various businesses and services have been provided by Web applications and Web pages, which can be easily used by using a Web (World Wide Web) browser. For example, shopping services are provided by displaying Web pages which introduce products on a user terminal to promote the user to select and order a product, settling the bill for the ordered product by the Web application by using a credit card number or the like, and delivering the product by a door-to-door delivery service. Users can enjoy various services, by using Web applications and Web pages.
On the other hand, such Web pages are frequently falsified, for example, a code to lead the user to a malicious Web page is embedded in the Web pages. Managers of Web pages are required to detect such falsifications early, and techniques of detecting Web-page falsifications have an increasing importance.
The Web-page falsification detection techniques include a technique of detecting falsification of a Web page, by calculating and storing characteristic information of the Web page in a storage module in advance, and comparing characteristic information of the Web page obtained directly before transmission with the characteristic information stored in advance in the storage module when the Web page is transmitted in response to a user's request.
In addition, there is a technique of detecting falsification of the Web page, in which the size of change in the Web page is used as an index, and it is determined that the Web page has been falsified, when change in the Web page is large.